The present invention relates to the production of wood pulp by the sulfate pulp process. The technology and objectives of the present invention are described in detail in U.S. Pat. No. 3,909,345, the disclosure of which is incorporated in its entirety herein by reference.
The '345 patent discusses and claims the use of surface active agents having the general formula EQU R[(C.sub.2 H.sub.4 O).sub.n (C.sub.3 H.sub.6 O).sub.m)]yH
as additives to sulfate cooking liquor aids for the purpose of obtaining higher yields of pulp from a given wood chip charge. The agents permit a greater effectiveness of the cooking process relative to chips which prior to that invention were considered rejects and not pulpable.
As the patent describes, wood chips derived primarily from coniferous (cypress, balsam, firs of various varieties, pines, etc.) are charged to a cooking vessel on a dry-weight basis and cooked for a predetermined time with a cooking liquor in a prescribed wood to liquor ratio (see Col. 2 of '345 patent). The cooking liquor is composed of various concentrations (depending on the wood comprising the chips and type pulp to be made) of sodium hydroxide and sodium sulfide.
The "cook" takes place at elevated pressures and temperatures (200.degree.-500.degree. F.) for periods ranging 1/2 to 10 hours.